The present invention relates to a device for aligning two planes spaced a distance from each other parallel relationship to each other. In particular, the present invention relates to a device for aligning optical measuring equipment.
In order to determine the optical correction that a patient requires, the patient views an image located twenty feet away while a series of lenses are positioned in front of the patient's eyes. To select the preferred correction the patient must indicate which lens or combination of lenses results in the clearest image. The lenses or lens combinations, sometimes referred as active zones, are usually located in an instrument referred to as a refractometer, Phoropter being one of the tradenames used on such devices. Different refractometer operators often arrive at slightly different sets of corrective lenses (a different eye glass prescription) for the same patient and the selected prescription may not be the optimum prescription for the patient. Additionally, the same patient may select a different combination of lenses at a different time. This inconsistency in prescription arrived at by operators or at different times can result from several different factors. However, it has been found that a part of the error results from not positioning the two sets of lenses in the refractometer parallel and in axial alignment with the image, i.e., the same distance from the image, being observed by the patient. This is a particularly difficult and time-consuming task as the refractometer and the image are frequently twenty feet apart.
Thus, there is a need for a simple, reliable and accurate method of aligning the refractometer parallel to and in axial alignment with the image. Further, this alignment method should be easily performed in as short a time as possible.